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The Digital Addressable Lighting Interface ('''DALI''') is a Digital Protocol for the controlling of Lighting in buildings, such as Electrical Ballast s and Dimmer s.

DALI was established as a successor for the still market dominating 1-10v and an Open Standard rival to Digital Signal Interface (DSI), on which it is based. DALI is standardized in accordance with International Electrotechnical Commission IEC 60929 , standard for fluorescent lamp ballasts.

Each piece of operating equipment with a DALI interface can be communicated with over DALI individually. Using a Bi-directional data exchange, a DALI controller can query and set the status of each light. As a standalone system, DALI can be operated with a maximum of 64 devices. Alternatively, DALI can be used as a subsystem via DALI Gateways .


ADVANTAGES

  • DALI is an open standard not exclusively owned by a single company.

  • It requires a two Bus wire bus for communication to devices on a DALI loop.

  • It doesn't insist the cabling is a "daisy-chain", "stars" and "T's" are perfectly acceptable giving the installers flexibility

  • The DALI System is not defined as SELV ( Safety Extra Low Voltage) and therefore can be run next to the mains carrying cables.

  • The DALI signal has a high SNR ( signal to noise ratio) which enables the signal to be exposed to a large amount of noise before the signal is destroyed.

  • The Baud ( or transmission speed) of DALI is low (1200hz) to reduce the need for Stub matching of the transmission lines and to reduce the complexity of the system

  • The maximum number of devices on a DALI loop is 64(An Advantage and Disadvantage) which is a manageable network size, smaller numbers may not be enough, while higher numbers become harder to commission and track

  • DALI has Group and Scene Commands to reduce the amount of information which is sent over a DALI loop. The use of these commands reduce network latency and allow for all devices to react within the same time. An example is "Group 1 goto 100%" or "Recall Scene 1"


Because it uses Differential Manchester Encoding it doesn't matter which way around the signal cable is wired, this makes installation more Foolproof .


DISADVANTAGES

  • In its infancy DALI had little tools available to commission the DALI devices

  • When addressed a DALI device is assigned a short address ( a number from 0-63) which becomes its unique address on the bus. When Installers or commissioners don't arrange the addresses in the devices in a logical order (for example following the flow of the building) replacement of faulty devices becomes confusing and time consuming

  • Being restricted to 64 addresses (six Bit s), DALI cannot be used in large installations without using another technology to Workaround the limitation.

  • Its slow communication speed (1200 Bits Per Second ) can mean a visible delay in large installations with a lot happening.

  • In Early models of some DALI Ballasts the number of times the the EEPROM could be rewritten was limited (200K - 3M times). In current generations of these DALI devices the number of EEPROM writes are unlimited.

  • There are few affordable portable test tools available for DALI, Portable tools are available from a number of companies and they range from $200EU upwards.

  • The data has to run on mains-rated cable, with 600v isolation and at least a 1mm cross-section rather than using a thinner data cable.

  • The volt-drop should be less than 2 volts from the start to the ends of the line thereby forcing disciplined planning by the installers.

  • The DALI signals are polarity sensitive, however most good manufacturers have circuitry inbuilt into their devices to overcome this issue and are usually labeled accordingly



EXTERNAL LINKS


Standards



Organisations

  • DALI action group , a working group set up by leading manufacturers and institutions in the field of digital lamp/luminaire control to promote DALI technology and applications



Manufacturers



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